In the UK there is one that is pay as you go. (You pay per letter/parcel received)
I just put in the minimum deposit and used that. As long as no one actually sends anything it is basically free apart from the deposit. (I think it was £5)
I just use a free PO Box service. Then the Whois guard on top.
There is Parrot OS Home edition which is marketed as privacy and security friendly.
I read somewhere someone had their encryption key on their phone / another server and had the server pull the key via ftp on boot. Then the server and encryption key is separated but can decrypt its self as long on the ftp server is available.
Edit - might have been unraid where the OS and data drivers are separate
You could have a look at rclone.
https://forums.unraid.net/topic/51633-plugin-rclone/
https://rclone.org/
Sound like you want the sync command.
rclone sync - Make source and dest identical, modifying destination only.
https://rclone.org/commands/rclone_sync/